Why You Shouldn't "Start a Diet" This Week
Hi {{ first name | there}},
Stop us if you've heard this one: It's January 2nd. You are motivated. You buy the kale. You book the class. By January 12th, you are tired, hungry, and convinced you lack "discipline".
Before we get into this week's briefing, a small reset: HEALTH HACK isn't a resolution plan, a challenge, or a new year guilt machine. It's a weekly attempt to reduce noise and make health easier to run under real life. You're not expected to read every issue, and you're definitely not expected to act on most things. If an idea fits your current week, use it. If not, note it and move on.
Now, here's the science: you don't lack discipline. You have circadian jetlag.
December's late nights, alcohol, and erratic meals can uncouple your Central Clock (brain, light-driven) from your Peripheral Clocks (liver/gut/pancreas, food-driven). When these clocks disagree, metabolic flexibility drops, hunger signaling gets noisier, and "willpower" (prefrontal cortex function) becomes harder to access.
The fix: this issue is not about restricting calories. It's about re-synchronizing timing cues.
We'll run a 72-hour protocol to bring your clocks back into agreement – then your nutrition and training plans start working again.
QUICK POLL
Which lever do you think matters most for getting January back on track?
⚠️ Next week, we’ll analyze the poll results and explain what actually matters physiologically.
LAST WEEK'S POLL RESULTS
What feels most broken right now?
27.3% Sleep timing (late nights)
25.5% Energy / focus ("brain fog")
22.7% Appetite / cravings
15.4% Alcohol recovery
9.1% Nothing – I'm a machine
-LONGEVITY PLAYBOOK-
If this helps, consider forwarding it to one person who's about to "start a diet" and silently hate their life by January 12.
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Your Body Is Still in December
Why January Diets Fail – and How to Re-Synchronize Your Biology in 72 Hours
January is not a motivation crisis. It's a timing mismatch.
Your central clock (SCN, suprachiasmatic nucleus) is set mostly by light. Your peripheral clocks are set heavily by food timing. In December, both drift – and they don't drift together.
When the clocks split, everything feels harder at once:
Hunger gets louder
Energy gets inconsistent
Focus gets unreliable
"Discipline" feels like it vanished
This isn't pathology. It's physiological lag.
A clean way to see it:
Your brain is on London time. Your liver is on New York time.
The best proof (not hype, actual human physiology)
A 2025 randomized clinical trial asked a brutal question: If sleep timing is "wrong", can meal timing still protect you?
Participants went through simulated night work / circadian misalignment, and researchers tested meal timing as a countermeasure. Result: daytime eating (despite mistimed sleep) mitigated adverse changes in cardiovascular risk factors. Same humans, same lab, same disruption – different timing cue, different outcome.
That's the thesis of this entire issue:
January isn't a calorie problem first. It's a timing cue problem first.
So here's the non-diet reset.
THE HEALTH HACK
The 72-Hour Circadian Re-Anchoring Protocol (No "Detox". No "Fasting".)
This is signal repair, not self-punishment.
1. Morning Light = Anchor the Central Clock (Huberman-grade specificity)
Don't say "lights on". That's indoor nonsense.
Get outdoor light soon after waking (even cloudy days count).
If you can, make it bright and early.
This is the strongest "start the day" signal your brain receives.
Why this matters: light timing changes downstream circadian signals (including melatonin timing). A 2025 Nature paper highlights how bright light exposure timing can meaningfully shift evening melatonin dynamics.
2. Meal Timing Compression = Anchor Peripheral Clocks (call it "Gut Rest")
We are not calling this fasting.
We're calling it what it is: a predictable daily schedule for your gut.
Keep a consistent first meal time.
Keep a consistent last meal time.
Create a daily gut-rest window (most people do best when dinner isn't late).
Why this matters: isocaloric time-restricted eating can shift circadian phase and metabolic markers – timing affects biology even when calories don't change.
3. Evening Temperature Cue = Trigger Sleep Onset (Walker mechanism)
Sleep onset is strongly associated with core body temperature dropping.
Evening heat exposure works because it creates rebound cooling afterwards.
A 2025 Sleep Health paper found before-bed hot-tub bathing was associated with better sleep outcomes in older adults – consistent with the rebound cooling model.
Run these 3 anchors for 72 hours.
The goal isn't "perfect health". The goal is clocks back in agreement.
MECHANISM EXPLAINER
Peripheral Clocks: Why You Don't Need a Detox – You Need a Schedule
Your liver doesn't need cleansing. It needs timing consistency.
Peripheral clocks regulate digestion and nutrient handling. When meals and sleep drift, those clocks desynchronize, and the body starts running mismatched programs.
Key line:
Your liver can be on New York time while your brain is on London time.
Fix the schedule. The system calms down.
THE REAL "DISCIPLINE" POINT
Willpower is a biological function of the prefrontal cortex. The PFC performs worse when sleep is unstable and glucose regulation is noisy.
Fix the biology and discipline becomes accessible again.
THE SUPPLEMENT
Glycine – The Temperature Lever Hiding in Plain Sight
Glycine isn't trendy.
That's exactly why it's useful.
Most sleep supplements try to sedate the brain. Glycine works differently – it supports one of the core physiological triggers of sleep onset: a drop in core body temperature.
Human data (including controlled trials) suggests that taking glycine before bed can improve subjective sleep quality and next-day fatigue/clarity, and part of the proposed mechanism is enhanced heat loss (peripheral vasodilation) that helps the body cool down.
In practice, the effective dose is not "a capsule". Most studies used grams, not milligrams.
What the studies suggest
Human trials using pre-sleep glycine (commonly 3 g) reported improvements in:
Subjective sleep quality
Next-day fatigue and "clear-headedness"
A mechanistic line of evidence suggests glycine can promote sleep by increasing peripheral blood flow and heat loss, tied to circadian control centers (SCN) in experimental work.
Mechanism (simple, not magical)
Glycine appears to support sleep onset by helping your body do what it already needs to do at night:
Increase peripheral vasodilation
Increase heat loss through the skin
Accelerate the cooling phase that precedes sleep
This is not a knockout pill. It is a friction reducer.
Dosing (the part most products get wrong)
Typical study range: 3–5 g in the evening
Why it matters: 500 mg capsules will not replicate the study effect.
A practical approach is starting at 3 g and only moving upward if tolerated.
Side effects
Glycine is generally well tolerated, but at gram-level doses some people report:
GI discomfort (bloating, nausea, soft stool)
Headache (uncommon)
If you are sensitive, start lower and titrate.
Who should skip this (quick filter)
Pregnant or breastfeeding (insufficient safety data for supplementation at gram doses)
Anyone with a medical condition or medication regimen where clinician oversight is appropriate (especially if sleep issues are severe or persistent)
Bottom line
Low risk.
Low cost.
Clean mechanism.
Glycine does not force sleep.
It supports the temperature shift your biology already uses to start it.
-PEPTIDE OF THE WEEK-
Selank
Nervous System Stabilization
(Experimental / Nootropic – Not Standard of Care)
Selank shows up frequently in biohacking circles, but it's important to be precise about why and how it's discussed here.
The evidence base is not robust by Western randomized controlled trial standards. Much of the human clinical literature is older, originates largely from Eastern Europe, and has not been widely replicated in large, modern randomized trials. That said, there are published human studies comparing Selank with anxiolytic comparators and reporting reductions in anxiety-related symptoms, alongside biochemical signals such as changes in enkephalin-related activity.
This places Selank firmly in the category of experimental neuropeptides – interesting, but not established.
Proposed Mechanisms (Hypotheses, Not Claims)
Selank is a synthetic peptide derived from a fragment of tuftsin, a naturally occurring immunomodulatory peptide. Its proposed effects sit at the intersection of stress signaling, neuropeptide modulation, and higher-order nervous system tone.
The main hypotheses discussed in the literature include:
Enkephalin modulation
Selank may influence endogenous opioid peptides (enkephalins), which play a role in stress response, emotional regulation, and pain perception. This could partially explain reported anxiolytic-like effects without overt sedation.GABAergic balance (indirect)
Unlike benzodiazepines, Selank does not directly activate GABA receptors. Any calming effect is thought to be modulatory rather than suppressive – important for avoiding cognitive dulling.BDNF-related signaling (theoretical)
Some preclinical and exploratory work suggests possible effects on neurotrophic signaling pathways (e.g., BDNF). This remains hypothetical and should not be framed as neuroplasticity enhancement.
Crucially:
There is no evidence that Selank "fixes" anxiety disorders, rewires the brain, or replaces behavioral or circadian interventions.
What Selank Is Not
❌ Not a sleep medication
❌ Not a metabolic intervention
❌ Not a substitute for light exposure, sleep regularity, or stress management
❌ Not a treatment for clinical anxiety or depression
Any perceived benefits are best understood as subtle nervous-system modulation, not symptom elimination.
Side Effects & Safety Considerations
Human data on side effects is limited, but reported issues (mostly anecdotal or from small studies) include:
Headache
Nasal irritation (common with intranasal use)
Mild dizziness or fatigue
Paradoxical agitation (rare but reported)
Unknowns matter more than knowns here:
Long-term human safety data is lacking
Dose–response relationships are not well established
Interactions with psychoactive medications are poorly studied
Why It Appears in This Issue
January stress is often nervous-system driven, not motivational. Selank fits the theme of this issue – nervous system stabilization – only when framed honestly as: "Here is the frontier, not the recommendation."
Behavioral timing cues (light, meals, temperature) remain the foundation. Selank, at best, sits at the outer edge of experimentation – not the center of the solution.
⚠️ Disclaimer: Selank is not FDA-approved. Human safety data is limited and uneven. Sourcing is the primary risk. Avoid if pregnant/breastfeeding, managing psychiatric illness, or taking psychoactive medications. Educational content only – not medical advice.
Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read in this newsletter.
-IN THE PRESS-
Quick Question
This issue is intentionally dense.
Rather than skimming headlines, we chose to go deep on one physiological theme (timing and nervous-system alignment). That's why we skipped the "IN THE PRESS" section this week.
Before we decide whether to bring it back regularly, we want your input.
Should we keep the "IN THE PRESS" section in future issues?
We aim to reduce noise, not add to it. Your vote helps decide what stays.
-SCIENTIFIC STUDIES-
Sleep is not just about how many hours you get – it is about sleep regularity/variability (timing and consistency), and that regularity shows up as a measurable risk signal for cardiometabolic disease.
Sleep regularity predicts major adverse cardiovascular events – even when sleep duration is "fine"
Device-measured sleep regularity in UK adults was associated with MACE risk; importantly, "enough hours" didn't necessarily erase the risk signal of irregular timing.
Phenome-wide analysis: objectively measured sleep traits linked to 172 diseases
A large UK Biobank actigraphy analysis linked objective sleep traits to 172 diseases over follow-up – reinforcing that regularity is not a wellness cliché; it's a disease-risk variable.
Sleep variability predicts risk signals for both OSA and hypertension (decentralized digital cohort)
Increased sleep variability predicted higher risk for OSA and hypertension markers, including a weekend variability signal.
Long-term sleep irregularity associated with blood pressure dynamics in older adults
A 2025 study examined sleep irregularity relationships with BP dynamics among older adults, adding weight to the "rhythm → cardiovascular burden" framing.
Magnesium bisglycinate RCT: 155 adults with poor sleep
A randomized, double-blind, placebo-controlled trial of magnesium bisglycinate (250 mg elemental Mg daily) assessed sleep quality and related outcomes. (We're not making this the main supplement this week – but it's a strong "evidence brick" for the sleep-stability theme.)
Remember!
💡 January Isn't Reinvention. It's Re-Synchronization.
If January feels harder than it "should", that's not a character flaw.
It's physiology catching up.
Your circadian system doesn't reset on January 1st. It responds to light, temperature, and timing – and it does so gradually. When those signals fall back into alignment, appetite regulation improves, sleep deepens, and decision-making gets easier without effort.
This is why discipline feels unreliable right now.
It's downstream of biology.
You don't need a new identity, a stricter plan, or more willpower this week. You need your clocks to agree again.
Once they do, most of the things people try to force in January start happening on their own.
Until next time,
Live longer. Upgrade wisely.
Rolf & the HEALTH HACK team
PS: If someone sent you this, you can subscribe here: https://newsletter.health-hack.com